Reheating temperatures: why 165 °F (73.9 °C) is the number for every leftover
Reheating looks like a lesser version of cooking, but the official target is not "warm" — it is 165 °F (73.9 °C), the same instant-kill temperature that governs poultry. Whether the leftover is lasagne, curry or roast chicken, the US rule is one number, verified with a thermometer at the coldest spot. This page collects the reheat rules, the one big exception (ham), and the UK's "steaming hot" framing.
Key takeaways
- All leftovers reheat to 165 °F (73.9 °C) — FoodSafety.gov prints 74 °C, Health Canada 74 °C (165 °F).
- Fully cooked ham reheats to 165 °F (73.9 °C), but ham packaged in USDA-inspected plants may be reheated to 140 °F (60 °C).
- Microwave reheating needs stirring, turning and standing time — then check temperature in several places.
- UK FSA: "steaming hot throughout," centre 70 °C for 2 minutes (or equivalent), and reheat only once.
The reheating table
| Food | Reheat to | Printed as |
|---|---|---|
| Leftovers — any type | 165 °F | 73.9 °C (FSIS) · 74 °C (FoodSafety.gov) · 74 °C (Health Canada) |
| Casseroles (meat and meatless) | 165 °F | 74 °C (FoodSafety.gov) |
| Fully cooked ham (general) | 165 °F | 73.9 °C (FSIS) · 74 °C (FoodSafety.gov) |
| Ham packaged in USDA-inspected plants | 140 °F | 60 °C (FoodSafety.gov chart note) |
| UK leftovers (FSA framing) | Steaming hot throughout — centre 70 °C held 2 minutes, or an official equivalent | |
Why is reheating's target the same as poultry's? Because a reheat must be a full kill step: during cooling, storage and serving, food may have picked up new bacteria, and some surviving spores can germinate once food sits in the danger zone (40–140 °F / 4.4–60 °C). A 165 °F (73.9 °C) reheat treats the entire dish as if it were freshly hazardous — which, bacteriologically, it is.
The ham exception, exactly as printed
FoodSafety.gov's chart carries one reheating footnote: cooked hams packaged in USDA-inspected plants may be reheated to 140 °F (60 °C), while other fully cooked hams go to 165 °F (74 °C). The logic is the plant's validated cook-and-seal process: the ham entered the package commercially sterile, so the reheat only needs to make it palatably hot rather than re-pasteurize it. For anything reheated from your own kitchen — a home-cooked ham included — 165 °F (73.9 °C) is the number. Both values are in the master chart and the lookup tool.
Oven, hob, air fryer, microwave
The appliance changes the technique, not the target. Oven and air-fryer reheats should be covered (moisture retention, even heating) and checked with a probe once the timer ends. Hob reheats need frequent stirring so the bottom does not scorch while the middle lags. The microwave is the trickiest: FSIS's microwave-cooking guidance exists because microwaves heat unevenly, leaving cold pockets where bacteria survive. The official techniques: cover the dish, stir or rotate midway, honour the standing time (heating continues after the beep), then verify 165 °F (73.9 °C) in several places — not just the centre. The UK FSA adds the same advice in its own words for lasagnes and similar: smaller portions reheat more evenly.
Reheat once — the rule most people break
The UK FSA states it directly: reheat leftovers only once. Every reheat cycle is a trip through the danger zone in both directions, and each cycle gives surviving spores another window to multiply; reheating also cannot destroy every heat-stable toxin some bacteria leave behind. The practical habit: portion leftovers before storing, so each container is reheated a single time. The clock that governs whether a reheat is even on the table — 2 hours to cool, 3–4 days fridge life, 48 hours in the UK — is covered in the leftover cooling rules.
Sauces, soups and gravies
FSIS's leftover guidance has a specific instruction for the liquid ones: bring soups, sauces and gravies to a rolling boil before serving — for these pourable foods, visible boiling is a legitimate official doneness cue, and a probe check of the stirred pot should show every spot at temperature. (Stir first: the surface boils long before the depths do.)
Educational reference, not personalized advice
Cooking for someone pregnant, elderly, very young or immunocompromised? Reheat thoroughly and follow the stricter guidance published by your health authority for their situation.
Related reading
- Leftover safety: 2-hour rule and 3–4 day window
- The complete safe internal temperature chart
- Fridge and freezer storage times chart
- What temp is chicken done? 165 °F (73.9 °C)
Sources verified: 2026-11-16. USDA FSIS — Leftovers and Food Safety · FoodSafety.gov chart (ham 140 °F / 60 °C note) · Health Canada · UK FSA — Cooking your food. Official numbers only — never rounded.